java - Libgdx Box2D Velocity is just not fast enough -

i have rectangle move fast ever reason faster velocity use still seems slow. doing wrong? have dropped circle above onto surface , tough play gravity comes down ballon...

some declarations

float velocity = 10000000f; static final float box_step=1/60f;   static final int box_velocity_iterations=6;   static final int box_position_iterations=2;   

gravity, tried , seem suck

world = new world(new vector2(0, -50), true);

the ground object moving onto

    //ground     bodydef groundbodydef =new bodydef();       groundbodydef.position.set(new vector2(0, camera.viewportheight * .08f));       body groundbody = world.createbody(groundbodydef);       polygonshape groundbox = new polygonshape();       groundbox.setasbox((camera.viewportwidth) * 2, camera.viewportheight * .08f);       groundbody.createfixture(groundbox, 0.0f);    

and here objects:

    //ball     bodydef = new bodydef();       bodydef.type = bodytype.dynamicbody;       bodydef.position.set(new vector2(camera.viewportwidth * .2f, camera.viewportheight * .75f));       body = world.createbody(bodydef);       circleshape dynamiccircle = new circleshape();       dynamiccircle.setradius(camera.viewportwidth * .035f);       fixturedef fixturedef = new fixturedef();       fixturedef.shape = dynamiccircle;       fixturedef.density = 0.5f;       fixturedef.friction = 0.5f;       fixturedef.restitution = 0.8f;       body.createfixture(fixturedef);      body.setlinearvelocity(0,-100);      //slime boy     bodydef bodyboxdef = new bodydef();       bodyboxdef.type = bodytype.dynamicbody;       bodyboxdef.position.set(new vector2(camera.viewportwidth * .08f,camera.viewportheight * .191f));       bodybox = world.createbody(bodyboxdef);       polygonshape slimebox = new polygonshape();       slimebox.setasbox(camera.viewportwidth * .04f, camera.viewportheight * .03f);     fixturedef fixtureslimedef = new fixturedef();       fixtureslimedef.shape = slimebox;       fixtureslimedef.density = 1.0f;       fixtureslimedef.friction = 0.0f;       fixtureslimedef.restitution = 0.0f;       bodybox.createfixture(fixtureslimedef);        debugrenderer = new box2ddebugrenderer();       body.applytorque(1000000000);     bodybox.setfixedrotation(true);     bodybox.setbullet(true); 

any 1 have suggestions speed movement in this?

i have been using screen 1280 720 saw other sources smaller better scaled down 640 260 still not preformance want. how small should go?

from box2d manual (section 2.2):

box2d tuned meters, kilograms, , seconds. can consider extents in meters. box2d works best when objects size of typical real world objects. example, barrel 1 meter tall. due limitations of floating point arithmetic, using box2d model movement of glaciers or dust particles not idea.

see https://stackoverflow.com/a/4556714/960524